📖 Theory & Concepts ▼

Reaction

2KMnO₄ + 5H₂C₂O₄ + 3H₂SO₄ → K₂SO₄ + 2MnSO₄ + 10CO₂↑ + 8H₂O
KMnO₄: Self-indicator (purple → colorless)
Endpoint: Persistent pale pink (last drop not decolorized)

Key Points

  • • Flask heated to ~60°C (reaction is slow at RT)
  • • First drops decolorize slowly; autocatalytic after Mn²⁺ forms
  • • n-factor: KMnO₄ = 5, H₂C₂O₄ = 2
Formula: N₁V₁/n₁ = N₂V₂/n₂

🎯 Objective

Determine the strength of KMnO₄ by titrating against standard oxalic acid (0.1N) using self-indication.

⚠️ Safety

  • Oxalic acid is toxic if swallowed and irritates skin/eyes — never pipette by mouth; wash any splashes.
  • dil. H₂SO₄ is corrosive; add acid to water. KMnO₄ is a strong oxidiser that stains skin/clothing brown.
  • Heat the acidified oxalic acid to only ~60 °C — above ~60 °C oxalic acid decomposes and the result is wrong.
  • Handle the hot flask with a holder; read the burette at eye level (the dark meniscus of KMnO₄ is read at the top).
  • Wear goggles; rinse apparatus and collect manganese waste for proper disposal.

Procedure

1. Fill burette with KMnO₄
2. Take 20mL oxalic acid + H₂SO₄
3. Heat flask to 60°C
4. Add KMnO₄ dropwise
5. Note persistent pink

Theory

Mn⁷⁺ → Mn²⁺ (gain 5e⁻)
C₂O₄²⁻ → 2CO₂ (lose 2e⁻)
Self-Indicator
Purple KMnO₄ → Colorless Mn²⁺

🔮 Predict before you titrate

Initial
0.0 mL
Current
0.0 mL
Used
0.0 mL
Burette (KMnO₄)
01020304050
20 mL Oxalic Acid (0.1N) + H₂SO₄
Heated to 60°C ♨️

📊 Readings

#InitialFinalVol
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Lab Notebook
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